The present disclosure relates to a method of acquiring and processing MRI data of neuronal resonance magnetic resonance imaging images.
It is obvious that communication is performed for delivering information between brain regions of a human. However, it is not still known how a specific brain region selectively delivers information to another brain region. In recent systems biology researches, a hypothesis is proposed that communication between brain regions is selectively performed through a frequency band selection filter from a signal of the entire brain. On the basis of this hypothesis, once a new imaging scheme capable of measuring a neuronal resonance frequency for the communication between the brain regions is developed, a communication mechanism between the brain regions, which is not yet well known, can be uncovered and have a significant effect on brain researches including psychology, mental science, and pathology.
A brain includes small regions responsible for numerous functions and these brain regions are structurally connected to each other. Most of brain functions such as actions, perceptions, and awareness are performed by fast and flexibly recombining a brain network. Recent researches partly reveal a dynamic, flexible and functional network configuration of the brain network on perceptions and awareness, selective concentration, and working memories. It has been known that oscillation characteristic and synchronization of neuronal spiking is associated with dynamic and flexible connectivity between brain regions. According to recent researches, it becomes revealed that neuronal oscillation and synchronization occurring in a specific frequency band controls a flow of information between the structurally connected brain regions and enables flexible and selective communication. However, it is not yet revealed through what mechanism the brain's flexible and selective communication tuned to a specific frequency band occurs in resting and active/stimulated states. Furthermore, according to numerous clinical data, it becomes known that patients of brain diseases including autism, schizophrenia, epilepsy, dementia, and Parkinson's disease have their neuronal synchronization characteristic changed in a wide frequency band and such abnormal neuronal synchronization may be a cause of symptoms (abnormal perceptions, actions, and movements, and the like) of those diseases.
Therefore, understanding of the selective communication mechanism between brain regions through the synchronization may allow a very important clue to treatment of the organic pathology and brain diseases to be discovered. Furthermore, developing a new imaging scheme capable of mapping a neuronal resonance characteristic for a wide band frequency used for brain region communication to a high resolution image may bring great ripple effects on academic, industrial and medical worlds related to medical and biological engineering.
On the other hand, a functional magnetic resonance imaging (fMRI) indirectly measures brain activities through interactions between neurons and blood flows, rather than measuring directly through a neuronal current. A couple of decades ago, it was shown for the first time that the fMRI might map non-invasively neuronal activities in the brain. Since then, the fMRI has had significant effects on neurology, psychology, and psychopathology.
The fMRI, unlike the existing MRI, is a mapping technique of a brain region by repetitively acquiring images when, and before and after there is external stimuli, and showing correlation with temporal patterns of the corresponding external stimuli through statistical processing. The fMRI is a nearly unique imaging scheme which is non-invasive and capable of mapping to a relatively high resolution image.
Even though the fMRI is a particular imaging scheme capable of non-invasively mapping neuronal activities, it uses an indirect measuring method through a blood flow change caused by neuronal activities rather than measuring directly a neuron's electrical signal. Endeavors to directly measure the neuron's electrical signal by using the MRI has been made for the last 10 years or more, but possibility thereof has been controversial.
About 10 years ago, it showed for the first time that the fMRI might be performed without external stimuli. This new fMRI technique is called as resting-state fMRI. A basic assumption of the resting-state fMRI is that if there is functional connectivity between two regions of the brain, temporal changes of MRI signals may have correlation with each other. The resting fMRI measures functional connectivity between brain regions. In the resting-state fMRI, a stimulation pattern used in the existing fMRI scheme is replaced with a temporal signal change of a seed region and a statistical analysis method is performed on whether rest of the brain regions shows a similar signal change to that of the corresponding brain region. In the resting-state fMRI scheme it is collectively measured whether certain brain regions (e.g., default mode network) are functionally connected. However, the existing fMRI scheme including the resting-state fMRI indirectly measures neuronal activities through blood flow dynamic reactions in a local region. The blood flow dynamic reaction is slow and has a time delay of about 4 seconds. Even though showing functional connectivity between brain regions, the resting-state fMRI does not show through what mechanism the brain regions selectively communicates. This is a fundamental limitation of the existing fMRI and explains why “frequency selective neuronal resonance” may not be confirmed with an existing method.
Furthermore, whether to be measurable a neuronal current in a living body by using the existing MRI imaging schemes has been controversial for the last ten years or more. Attempts to directly measure the neuronal current have been continuously made several times. Even though promising results have been continuously shown in phantom, cell culture, and theoretical calculation researches, whether to be measurable neuronal current in a living body by using MRI has been controversial for ten years or more. Researchers in the field of the art all agree on a fact that the neuronal current causes a magnetic field change on the periphery and the change may be measured with MRI. However, many researchers insist that it is very difficult to consistently measure the magnetic change in a living body with MRI because an MRI signal generated by a change of the magnetic field, which is generated by the neuronal current, is too small.
MRI schemes for directly detecting the neuron's electrical signal are largely divided into two approaches. A first approach is to use periodic stimulation having a uniform time period and measure the neuron's electrical signal by acquiring an MRI signal right after stimulation is completed (i.e., before blood flow dynamic reaction is generated). A second approach is to raise temporal resolution 100 ms) of MRI image acquisition and search for a component resonated with a frequency of external stimuli through Fourier transform. All the two approaches depend on a period or a frequency of external stimuli and do not consider the natural frequency of the neuron. Whether to detect a neuronal current signal is still controversial with respect to all the existing MRI imaging schemes including the two approaches.